Selective dorsal rhizotomy (SDR) is a spinal surgery that permanently reduces muscle tightness, or spasticity, in the legs. It works by cutting specific sensory nerve fibers in the lower spine that send abnormal signals to muscles, causing them to stay tense. SDR is most commonly performed on children with cerebral palsy, though adults can also benefit.
How SDR Works
Spasticity happens when the communication loop between your muscles and spinal cord goes wrong. Sensory nerves carry signals from the muscles back to the spinal cord, and in conditions like cerebral palsy, those signals are abnormal. The spinal cord responds by telling the muscles to tighten constantly. SDR interrupts this loop at its source.
During the procedure, a neurosurgeon opens a small section of the lower spine and uses a surgical microscope to access the sensory (dorsal) nerve roots. Each nerve root is then separated into its individual strands, called rootlets. One by one, roughly 15 to 25 rootlets on each side of the spine are stimulated with a small electrical current while a neurologist monitors how the leg muscles respond. Rootlets that produce abnormal, exaggerated muscle responses are identified and cut. The ones that respond normally are left intact. This selective approach is what separates SDR from older, less precise procedures. It reduces spasticity while preserving useful sensation and motor control.
Who Is a Candidate
The strongest candidates for SDR are children with bilateral spastic cerebral palsy, meaning spasticity affects both legs. A worldwide survey of SDR centers found universal agreement that the best-suited patients are those classified at GMFCS levels II or III, a scale that describes how independently a child can move. Level II children walk independently but have limitations with uneven surfaces or long distances. Level III children typically need a handheld mobility device.
Most centers consider the standard age range to be 5 to 7 years old, though some neurosurgeons advocate for earlier intervention. The team at St. Louis Children’s Hospital has performed SDR on children as young as 2 and 3, reporting that the procedure is feasible and safe at those ages. Adequate leg strength, some existing motor control, and reliable access to post-operative physical therapy are also essential requirements. Children undergo physical assessments, gross motor testing, and gait analysis before being approved for surgery.
What Happens During Surgery
SDR can be performed using two main techniques. The multi-level approach involves opening several vertebrae in the lower spine to access nerve roots where they exit the spinal column. The single-level approach uses a smaller incision at just one vertebral level, near the bottom of the spinal cord. The single-level procedure requires more surgical skill and takes longer, but it involves less muscle dissection and a shorter hospital stay: about 3.4 days compared to 5.2 days for the multi-level approach. Functional outcomes at one year are similar regardless of which technique is used, and there are no significant differences in post-operative pain or time to get moving again.
How Much Spasticity Is Reduced
The reductions in muscle tightness after SDR are substantial. In a study of children with spastic cerebral palsy, spasticity in the hip flexors dropped by about 63%, hamstring tightness fell by 61%, and calf muscle spasticity decreased by roughly 42%, all measured 12 months after surgery.
These changes translate into real functional gains. At one year post-surgery, 58.5% of patients improved by at least one level on the GMFCS mobility scale, and 12.2% improved by two levels. Over three-quarters of patients showed measurable improvement in their ability to walk. Children under 10 saw the most dramatic gains: nearly 47% improved their GMFCS level by at least one, compared to none of the older participants in that particular study. Children with more severe baseline impairment (GMFCS levels IV and V) also showed high rates of improvement, with 77.7% gaining function at 12 months.
Long-Term Durability
One of the most important questions families ask is whether the benefits last. A 20-year follow-up study found that the functional improvements seen one year after SDR were still present two decades later. Because the nerve rootlets are physically cut, spasticity does not return in the treated muscles. This permanence is a defining advantage of SDR over treatments like Botox injections or oral medications, which require repeated dosing and wear off over time.
SDR for Adults
Though SDR is primarily a pediatric surgery, adults with cerebral palsy can also undergo the procedure. The goals shift somewhat: rather than building new motor skills during development, adult SDR typically aims to halt or reverse declining mobility and reduce chronic pain.
In a study of 64 adults who received SDR, 91% reported improved walking quality, 81% reported better standing, and 88% found it easier to exercise. Muscle and joint pain improved in 64% of patients. Overall, 23% gained a higher level of ambulatory function, 70% maintained their pre-surgery level, and just over 7% experienced some decline. Outcomes were less favorable in patients over 40, so age is a factor in the decision-making process.
Risks and Complications
SDR is generally safe, but it carries real risks, particularly to spinal structure. The most common complication category involves the spine itself. In a systematic review of over 1,000 patients, scoliosis developed in about 20.5%, excessive lower-back curvature (hyperlordosis) in 18.2%, stress fractures of the vertebrae (spondylolysis) in 9.5%, and forward curvature of the upper spine (kyphosis) in 8.4%. These structural changes can develop over the years following surgery, which is why long-term orthopedic monitoring matters.
Neurological complications are less common but still notable. Constipation affected 14.4% of patients studied, sensory changes like altered feeling in the legs occurred in 8.2%, and urinary incontinence was reported in 6% of cases. Hip subluxation, where the hip joint partially slips out of place, appeared in a smaller subset of patients.
Post-Operative Rehabilitation
SDR is not a one-day fix. The surgery removes spasticity, but the muscles and movement patterns that developed around that spasticity need to be retrained. Physical therapy after SDR is intensive and typically lasts about a year, starting within the first day or two after surgery.
Early sessions focus on basic mobilization: changing positions, gentle range-of-motion exercises, and learning to sit and lie in new postures now that the muscles are no longer pulling tight. The intensity is highest in the first few months. Common protocols involve four to five therapy sessions per week, each lasting 45 minutes to an hour, during the initial three to six months. After that, frequency gradually tapers to one to three sessions per week for the remainder of the first year. Some programs continue at a lower frequency for up to 18 months.
There is no single standardized protocol, and the specifics vary by center and by the child’s needs. What is consistent across programs is the expectation that rehabilitation will be rigorous and sustained. The therapy is not optional or supplementary. It is the mechanism through which the surgical reduction in spasticity gets converted into improved walking, balance, and daily function. Families considering SDR should plan for this commitment before scheduling the procedure.